BEAM BRIDGES. is a horizontal piece of structure that spans across an opening. A beam bridge is often supported by vertical piers that

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1 ACTIVITY GUIDE

2 At the Center for Architecture, we love exploring bridges with our students! Bridges are amazing structures that showcase thoughtful engineering and creative thinking. This booklet will introduce you to four types of bridges: beam, truss, arch, and suspension. Each page is illustrated with diagrams and body exercises to help you understand the structural forces at work in each bridge. The pushing force of compression is shown in orange, and the pulling force of tension in green. Once you ve learned these bridge basics, try designing your own!

3 BEAM BRIDGES A beam is a horizontal piece of structure that s across an opening. A beam bridge is often supported by vertical piers that compression help carry the weight of traffic on the bridge and shorten the distance it must. If the weight is too heavy, or the too long, the beam will bend. This bending creates the forces of compression ( pushing ) and tension ( pulling ) in the beam. beam tension beam Form a beam bridge with two friends. Can you feel tension and compression across your? What can you do to keep from bending? pier footing

4 TRUSS BRIDGES A truss is a structure made up of triangles. Triangles are naturally strong shapes, so truss bridges can carry more weight and further than beam bridges. Each piece of a truss is either being pushed ( compressed ) or pulled ( tensed ), but Test out the strength of triangles. Form a rectangular structure with a friend and have someone push on you from the side. What happens? not both, so a truss doesn t bend easily. It is also much lighter than a beam since it is made up of individual pieces instead of solid material. truss Now create a truss with your friend and try it again. Can you feel the tension and compression in your legs as they try to resist this force and keep your structure strong?

5 ARCH BRIDGES An arch is a structure shaped like a semi-circle. When the roadway hangs down from the arch, it is called When a bridge roadway sits on top of an arch, the weight of traffic pushes down on the arch. This pushing force ( compression ) is carried along the curve of the arch to the abutments at each end. a bowstring arch bridge. The roadway takes the place of the abutments and works in tension, pulling in on both ends of the arch to keep its shape. Abutments are heavy supports that push back in from both sides to make sure the arch doesn t flatten out or collapse. Try pushing together the sides of this booklet to create an arch. Your hands are acting as the abutments. What happens if you let go? abutment What could you add across the bottom of this arch to help keep its shape by pulling in on both sides?

6 SUSPENSION BRIDGES In a suspension bridge, strong towers support a main cable that is pulled tightly at each end by heavy anchorages. Straight suspender cables hang from the main cable and hold and lift the roadway along its. This unique design allows suspension bridges to the furthest of all bridge types. A cable-stayed bridge is a new form of suspension bridge Trusses are often used to stiffen the long roadways of that has diagonal cables stretching directly these bridges. Suspension bridge cables are always in tension (pulling). The towers, however, are in compression and must stand strong to resist the downward pull of the main cable. from a central tower to the roadway, with no main cable. These bridges don t as far as classic suspension bridges, but use less material and are less expensive to build. side main side suspender cable main cable tower Model a suspension bridge with your friends to feel the tension and compression at work! anchorage footing

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